Historically, toxic baits for controlling crawling insects such as cockroaches have been water-based. With cockroaches especially, water is presumed necessary for good bait performance. Unfortunately, water-based bait products rapidly lose effectiveness due to water loss, rancidity, break-down of active ingredients and other factors. Studies of water-based paste baits have confirmed that water loss, repellent properties of active ingredients, and insecticide resistance are the most important factors affecting bait performance. Appel, A. G., J. Econ Entomol. 85 (4): 1176–1183 (1992), Robinson, W. H., Proceedings of the National Conference on Urban Entomology 77–91 (1992), and Rust, N. K., “Managing Household Pests”, in Advances in Urban Pest Management, G. W. Bennett and M. Owens (eds), Van Norstrand Reinhold, N.Y. 335–368 (1986).
One approach to improve on water-based insecticide products has been to use a dust or a paste composition which includes a so-called water powder with the insecticide. This water powder is water encapsulated with hydrogenated soybean oil. Such a product is described in U.S. Pat. No. 5,820,855. Unfortunately, dust compositions have disadvantages such as drifting of the material when applied.
Water-free fat-based pest bait products are described in U.S. Pat. Nos. 5,464,613 and 5,464,613. These compositions are paste forms and include as a major ingredient a fat-based carrier. Although paste products do not drift, they are difficult to apply and require an applicator in applying pastes in cracks and crevices or into voids. Another disadvantage of the paste, water-free products are that they are not as fast-acting as water-based products, especially against cockroaches.
Acephate is a very desirable insecticide, particularly in killing cockroaches. Acephate's desirability is based on the fact that there is no known insecticide resistance and because it has a very low mammalian toxicity. However, acephate is not stable in water-based matrices over time. Although acephate has been described in the above water-free, fat-based patents, it is not currently used as an active ingredient in any commercially available cockroach bait. There is thus a need for improved rapid acting, water-based baits that utilize water-sensitive insecticides.